Andersson, Christian

Abstract [en]

Fermentation is one of the oldest utilizations of microorganisms known to man. Depending on the physical and chemical conditions as well as on the microorganism used, a wide variety of compounds can be produced. Since fermentation uses renewable resources instead of fossil fuels product manufacturing, it does not contribute to the green house effect and the interest in the process has increased greatly during the last decades. This thesis is an investigation of the fermentative capabilities of the E. coli strain AFP184. It includes the set up of a bioreactor, operation of a biotechnical process and the following chemical and biological analysis. The idea behind the thesis was to investigate how well the AFP184-organism is able to utilize five carbons sugar, e.g. xylose, as carbon source for succinic acid production compared to similar fermentations utilizing a sugar feed consisting of pure glucose. A fermentation process developed by LEC TECH Inc. was initially used to start the experiment. Samples taken during fermentation were analyzed by HPLC and the succinic acid production was finally calculated from the peak area absorbances by the TotalChrome software and a MATLAB script. The results reached concentrations of approximately 30 g/l, which is slightly lower than results obtained by LEC TECH Inc. It is expected that the main reason for this is a lack of viable cells. To improve succinic acid production the optimal viable cell mass must be found. This can be done by conducting an aerobic fermentation and establish the time it takes for the particular cell culture to reach a stationary phase on the growth curve. The flowrate of carbon dioxide is also of importance for succinic acid production. The more viable cells in the reactor mixture the more carbon dioxide can be utilized for acid production, and thus when the optimal growth time has been established, the flowrate of carbon dioxide needs to be investigated. Another parameter that ought to be examined is to what extent the organism utilized xylose for succinic acid formation. This can be done by HPLC techniques.